WASHINGTON (AP) — Are the nation’s students and professors intolerant when it comes to free speech on college campuses?

Students and academics insist the golden rule is for the speech to go on as long as violence can be prevented as a Senate panel examined whether free speech on college campuses is becoming threatened.

The hearing came after two high-profile speeches at the University of California at Berkeley were canceled amid fears of violent student protests. More recently, a commencement address by the No. 2 Senate Republican, John Cornyn of Texas, was canceled after opposition from students at the historically black university where he was scheduled to speak.

Eugene Volokh, a professor at the UCLA School of Law, said what he described as a “heckler’s veto” should not be allowed.

“I think the answer is to make sure they don’t create a disturbance and to threaten them with punishment, meaningful punishment, if they don’t have their way,” Volokh said. “If thugs learn that all they need to do in order to suppress speech is to threaten violence, then there will be more such threats.”

But Democratic Sen. Dianne Feinstein of California said the universities can’t always deal with the fallout when anarchists and others respond to the appearance of a speaker they oppose. “You don’t think we learned a lesson at Kent State way back when?” Feinstein said at one point.

In 1970, National Guardsmen opened fire on protesters of the Vietnam War at Kent State in Ohio. Four students died and nine others were wounded.

The witnesses on Tuesday acknowledged that university officials at times have a difficult choice to make.

“These are always judgment calls that are made,” said Frederick M. Lawrence, secretary and CEO of the Phi Beta Kappa Society, the oldest honor society for the liberal arts and sciences in the United States. “I think the way to start with this is a strong presumption in favor of the speech.”

Republicans on the committee were overwhelmingly critical of the cancellations. Republican Sen. Chuck Grassley of Iowa said that on too many campuses, free speech appears to have been “sacrificed at the altar of political correctness.”

Grassley said college students vote and when universities suppress speech they may “cause and exacerbate the political polarization that is so widely lamented in our society.”